That URI is an absolute URL, so use that as your next query to get the subfolders of the root folder. This will return your "Contas a Ordem" folder, as well as the default "Forms" folder. But if you look at the properties on your "Contas a Ordem" folder, you will see that it also has a Folders.__deferred.uri property that you can use in your next query to get the subfolders of "Contas a Ordem".

And once you get those, you will see that they each also have a Folders.__deferred.uri property that you can use to get their subfolders, and so on and so on.

Incidentally, you will also see that all the folder objects returned also have a Files.__deferred.uri property that will give you a URI to get the files inside that folder.

Requesting the Items collection for the list will bring back all items and folders regardless of what folder they are in. You can use the FileSystemObjectType or ContentType property to determine if the item is or is not a folder. In the example below I'm using the FileSystemObjectType.